Heretofore, interfaces have been used that interface a control module to other modules. However, no universal interface for interfacing a plurality of communications protocol was available until the system and method particularly contemplated by the invention described and claimed in U.S. patent application Ser. No. 09/814,221, entitled “Slave ASIC”, incorporated herein by reference in its entirety.
Nevertheless, there is a need for an improved system for and method of interfacing expansion modules with programmable logic controllers (PLCs). Further, there is a need to detect the presence of an error on the first byte of a communication signal to prevent writing out invalid data.